Across 18 years, Mariano Rivera put together a 206 ERA+ over the entirety of his career. That's the best in the history of the game, even including starting pitchers. Not only is it enough that he has the most saves in baseball, but he is also the greatest of all time. Saves don't always display an accurate portrayal of a pitcher's talents, but here they absolutely do.
Here is a list of Mo's ERA+ per season ranked from best to worst. Highlighted in yellow are the best seasons by other relievers. That is how good he has been. Not only is he the best of all time, but he's put up one of the best single seasons as a reliever. A few have been better over a single season, but they all fall far behind him in terms of how consistent he has been.
In 2008, Rivera only had 39 saves, but he also had the second highest strikeout rate of his career at 9.8 K/9. He had the second lowest ERA (1.40) of his career and lowest WHIP (0.665). He had his lowest H/9 rate (5.2) and his lowest walk rate (0.8), which amounted to a total of 6 (!) walks As a testament to how good Mariano Rivera is and incase anyone forgets:
- Trevor Hoffman had an 18 year career and his best season was in 1998, where he put up a 265 ERA+ for the Padres. His best season would be equivalent to Mo's fourth best season. The player with the second highest career saves only has a career 141 ERA+
- Jonathan Papelbon put up a ridiculous 517 ERA+ in 2006, but his next highest, 257, is only equal to Rivera's 5th best year. For his career, he has only a 192 ERA+ and his last three seasons have been his three worst.
- Billy Wagner has 422 career saves and a career 187 ERA+ through a 16 year career. In 2005 he had his best season with the Phillies and put up a 293 ERA+, and as impressive as that was, it would still only be Mo's third best season.
- John Franco pitched for 21 seasons and in that time he accumulated a 138 ERA+ and in his best season, in 1988, he had a 230 ERA+. That number only makes it to Mariano Rivera's 12th best season.
- Lee Smith was once the career saves leader in baseball, with 478. In an 18 year career he had a 132 ERA+ for his career and in his best year, 1983 for the Cubs, he had a 229 ERA+ and that was only Rivera's 12th best season. That's just silly.
- Eric Gagne won the Cy Young Award in 2003 and put up a 337 ERA+, which was actually higher than Mo, but for his career he only had a 119 ERA+ and last saw the majors at 32 in 2008, while Rivera had his best year.
- Dennis Eckersley had a ridiculous 1990 season where he had a 603 ERA+, but he won the Cy Young Award and MVP Award in 1992 with only a 195 ERA+. That would be Mariano Rivera's sixth worst season of his career. The Hall of Famer still only had a 116 ERA+ for his career, though he did spend the first 14 years of his 24 year career as a starter.
He has outperformed Hall of Fame relievers like Rollie Fingers and Goose Gossage, so it's clear that they'll all have to move down a step when Mariano eventually joins them. There is no one greater.